a2kit 4.4.2

//! ## Low level Apple images
//! 
//! This contains common components for images that represent Apple tracks
//! as nibbles, bits, or fluxes, most notably WOZ images.
//! 
//! ### Emulator vs. Editor
//! 
//! The WOZ image format is designed to allow emulators to run
//! copy protected software.  The trick is to make the emulation
//! accurate enough so that all relevant details of the software's
//! interaction with the disk hardware is captured.
//! 
//! However, a2kit is not an emulator, it is an editor.
//! Therefore some of the WOZ protocols that are
//! conceived with emulators in mind are not strictly adhered to.
//! 
//! ### Cross-Track Synchronization
//! 
//! The position of the head over the disk is maintained internally
//! for the lifetime of the `DiskImage` trait object.  Emulated time
//! affects the state of the `TrackEngine` and `FluxCells` objects.
//! It is possible for cross-track synchronization to be spoiled by certain
//! pathological write operations.
//! 
//! ### Quarter Tracks
//! 
//! In terms of the CLI, the user can request quarter tracks using quarter-decimals.
//! The `DiskImage` trait uses instead the `img::Track` abstraction, which allows
//! the stepper-motor position to be explicitly specified.
//! 
//! In this situation the addressing of a track can be confusing.
//! The various schemes are given as follows:
//! 
//! disk | track | cyl,head | motor,head | TMAP index
//! -----|-------|----------|------------|-----------
//! 5.25 | 0..35 | (0..35, 0..1) | (0..140, 0..1) | 0..140
//! 5.25 | 0..40 | (0..40, 0..1) | (0..160, 0..1) | 0..160
//! 3.5-400K | 0..80 | (0..80, 0..1) | (0..80, 0..1) | 0..80
//! 3.5-800K | 0..160 | (0..80, 0..2) | (0..80, 0..2) | 0..160
//! 
//! ### Blank Tracks
//! 
//! An emulator is supposed to serve up fake bits if the head is on a blank
//! track, and continue to maintain the head state.
//! As an editor, a2kit will return `BlankTrack` instead.
//! 
//! ### Fake Bits
//! 
//! Fake bits will be generated if the `TrackEngine` method is set to emulate.
//! 
//! ### Drive Motor and Soft Switches
//! 
//! The delayed shut-down of the drive motor is not handled.  Side effects
//! of various disk-related soft switches are not handled.  This is
//! because a2kit has no notion of such things.  The track object is
//! merely serving up bits on demand, subject to certain filters.
//! 
//! ### Logic State Sequencer
//! 
//! For writing, the LSS is never used, bits and flux transitions are positioned "by hand."
//! For reading, the LSS is emulated down to the cycle level if `Method==Emulate`.
//! If `Method==Fast`, reading is carried out using a simplified model.
//! 
//! ### Flux tracks
//! 
//! The engine can read and write flux tracks.  Flux tracks can be created at image
//! creation time, but once a disk image exists, bit-stream tracks remain bit-stream tracks,
//! and flux-tracks remain flux-tracks.

use std::fmt::Write;
use std::u8;
use super::{Track,SectorHood,DiskKind};
use super::tracks::{DiskFormat,ZoneFormat};

use crate::{STDRESULT,DYNERR};
const RCH: &str = "unreachable was reached";

pub const INFO_ID: u32 = u32::from_le_bytes(*b"INFO");
pub const TMAP_ID: u32 = u32::from_le_bytes(*b"TMAP");
pub const TRKS_ID: u32 = u32::from_le_bytes(*b"TRKS");
pub const FLUX_ID: u32 = u32::from_le_bytes(*b"FLUX");
pub const WRIT_ID: u32 = u32::from_le_bytes(*b"WRIT");
pub const META_ID: u32 = u32::from_le_bytes(*b"META");
pub const ALLOWED_TRACKS_525: [usize;1] = [35];

const CRC32_TAB: [u32;256] = [
	0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f,
	0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
	0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2,
	0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
	0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
	0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
	0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c,
	0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
	0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423,
	0xcfba9599, 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
	0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190, 0x01db7106,
	0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
	0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d,
	0x91646c97, 0xe6635c01, 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
	0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
	0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
	0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7,
	0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
	0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa,
	0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
	0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81,
	0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
	0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683, 0xe3630b12, 0x94643b84,
	0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
	0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
	0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
	0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8, 0xa1d1937e,
	0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
	0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55,
	0x316e8eef, 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
	0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28,
	0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
	0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f,
	0x72076785, 0x05005713, 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
	0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
	0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
	0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69,
	0x616bffd3, 0x166ccf45, 0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
	0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc,
	0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
	0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693,
	0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
	0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
];

/// Calculate the checksum for the WOZ data in `buf`
pub fn crc32(crc_seed: u32, buf: &Vec<u8>) -> u32
{
	let mut crc = crc_seed ^ !(0 as u32);
	for p in buf {
	    crc = CRC32_TAB[((crc ^ *p as u32) & 0xFF) as usize] ^ (crc >> 8);
    }
	return crc ^ !(0 as u32);
}

/// Get the next WOZ metadata chunk.  Return tuple (ptr,id,Option(chunk)).
/// Here `ptr` is the index to the subsequent chunk, which can be passed back in.
/// The returned chunk buffer includes the id and size in the first 8 bytes.
/// The returned pattern can be matched as follows.
/// (0,id,Some) => good chunk and there are no more chunks.
/// (ptr,id,Some) => good chunk and there is another chunk.
/// (0,id,None) => unknown chunk and there are no more chunks.
/// (ptr,id,None) => unknown chunk and there is another chunk.
/// The caller should ignore unknown chunks and keep going until no more chunks.
/// The `DiskStruct` trait can be used to unpack the chunk at higher levels.
pub fn get_next_chunk(ptr: usize,buf: &[u8]) -> (usize,u32,Option<Vec<u8>>) {
	// this can only evaluate true on the first call
	if ptr+8 > buf.len() {
		return (0,0,None);
	}
	let id = u32::from_le_bytes([buf[ptr],buf[ptr+1],buf[ptr+2],buf[ptr+3]]);
	let size = u32::from_le_bytes([buf[ptr+4],buf[ptr+5],buf[ptr+6],buf[ptr+7]]);
	let end = ptr + 8 + size as usize;
	let mut next = end;
	// if size puts us beyond end of file this is not a good chunk, and also no more chunks
	if end > buf.len() {
		return (0,0,None);
	}
	// if there is not enough room for the next chunk header then no more chunks
	if next+8 > buf.len() {
		next = 0;
	}
	if id==0 && size==0 {
		log::trace!("encountered nulls trailing previous chunk");
	} else {
		log::debug!("found chunk id {:08X}/{}, at offset {}, next offset {}",id,String::from_utf8_lossy(&u32::to_le_bytes(id)),ptr,next);
	}
	match id {
		INFO_ID | TMAP_ID | TRKS_ID | FLUX_ID | WRIT_ID | META_ID => {
			// found something
			return (next,id,Some(buf[ptr..end].to_vec()));
		}
		_ => {
			// unknown chunk type
			return (next,id,None);
		}
	}
}

/// Check that `trk` is valid for the given `kind`, does not examine the medium.
fn verify_track_key(trk: Track,kind: &DiskKind) -> STDRESULT {
	let trouble = match *kind {
		DiskKind::D525(_) => {
			match trk {
				Track::Num(t) => t > 34,
				Track::CH((c,h)) => c > 34 || h > 0,
				Track::Motor((m,h)) => m > 159 || h > 0
			}
		},
		DiskKind::D35(layout) if layout.sides[0]==1 => {
			match trk {
				Track::Num(t) => t > 79,
				Track::CH((c,h)) => c > 79 || h > 0,
				Track::Motor((m,h)) => m > 79 || h > 0
			}

		},
		DiskKind::D35(layout) if layout.sides[0]==2 => {
			match trk {
				Track::Num(t) => t > 159,
				Track::CH((c,h)) => c > 79 || h > 1,
				Track::Motor((m,h)) => m > 79 || h > 1
			}
		},
		_ => panic!("unsupported disk kind")
	};
	if trouble {
		log::error!("{} is out of range",trk);
		Err(Box::new(super::Error::TrackNotFound))
	} else {
		Ok(())
	}
}

/// return [motor,head,width]
pub fn get_motor_pos(trk: Track,kind: &DiskKind) -> Result<[usize;3],DYNERR> {
	verify_track_key(trk.clone(),kind)?;
	let ans = match *kind {
		DiskKind::D525(_) => {
			match trk {
				Track::Num(t) => [t*4,0,4],
				Track::CH((c,_)) => [c*4,0,4],
				Track::Motor((m,_)) => [m,0,4]
			}
		},
		DiskKind::D35(layout) if layout.sides[0]==1 => {
			match trk {
				Track::Num(t) => [t,0,1],
				Track::CH((c,_)) => [c,0,1],
				Track::Motor((m,_)) => [m,0,1]
			}
		},
		DiskKind::D35(layout) if layout.sides[0]==2 => {
			match trk {
				Track::Num(t) => [t/2,t%2,1],
				Track::CH((c,h)) => [c,h,1],
				Track::Motor((m,h)) => [m,h,1]
			}
		},
		_ => panic!("unsupported disk kind")
	};
	Ok(ans)
}

/// Get the TMAP index, after verifying the `trk` is valid for this `kind`.
pub fn get_tmap_index(trk: Track,kind: &DiskKind) -> Result<usize,DYNERR> {
	verify_track_key(trk.clone(),kind)?;
	let tmap_idx = match *kind {
		DiskKind::D525(_) => {
			match trk {
				Track::Num(t) => t*4,
				Track::CH((c,_)) => c*4,
				Track::Motor((m,_)) => m
			}
		},
		DiskKind::D35(layout) if layout.sides[0]==1 => {
			match trk {
				Track::Num(t) => t*2,
				Track::CH((c,_)) => c*2,
				Track::Motor((m,_)) => m*2
			}
		},
		DiskKind::D35(layout) if layout.sides[0]==2 => {
			match trk {
				Track::Num(t) => t,
				Track::CH((c,h)) => c*2+h,
				Track::Motor((m,h)) => m*2+h
			}
		},
		_ => panic!("unsupported disk kind")
	};
	Ok(tmap_idx)
}

/// Create a track key for this TMAP index.
pub fn trk_from_tmap_idx(tmap_idx: usize,kind: &DiskKind) -> Track {
	match *kind {
		DiskKind::D525(_) => Track::Motor((tmap_idx,0)),
		DiskKind::D35(layout) if layout.sides[0]==1 => Track::Motor((tmap_idx/2,0)),
		DiskKind::D35(layout) if layout.sides[0]==2 => Track::Motor((tmap_idx/2,tmap_idx%2)),
		_ => panic!("unsupported disk kind")
	}
}

/// Get the sector neighborhood for this TMAP index.
/// Can panic if arguments are invalid.
pub fn get_sector_hood(vol: u8,tmap_idx: usize,kind: &DiskKind,zone: usize) -> SectorHood {
	match *kind {
		DiskKind::D525(_) => SectorHood::a2_525(vol,(tmap_idx as u8+1)/4),
		DiskKind::D35(layout) => SectorHood::a2_35(
			(tmap_idx / 2) as u8,
			(tmap_idx % layout.sides[zone]) as u8
		),
		_ => panic!("unsupported disk kind")
	}
}

/// This will employ certain rules in an attempt to produce "nice" motor stops
/// for use in generating a track array for user consumption, or for estimating
/// the actual capacity of the disk as formatted.
/// There is an assumption that the set of important tracks are mostly whole tracks apart.
/// This should only be used for 5.25 inch disks.
pub fn find_motor_stops(tmap: &[u8],maybe_fmap: Option<&[u8]>) -> Vec<usize> {
	let mut ans = Vec::new();
	let mut set = [0xff,0xff,0xff,0xff];
	for motor in 0..160 {
		set.rotate_left(1);
		set[3] = match maybe_fmap {
			Some(fmap) if fmap[motor] !=0xff => fmap[motor],
			_ => tmap[motor]
		};
		if motor%4 == 2 {
			match set {
				[_,w,_,h] if w!=0xff && h!=0xff => {
					if w == h {
						ans.push(motor-2);
					} else {
						ans.push(motor-2);
						ans.push(motor);
					}
				},
				[qm,0xff,qp,h] => {
					if h != 0xff {
						ans.push(motor);
					} else if qp != 0xff {
						ans.push(motor-1);
					} else if qm != 0xff {
						ans.push(motor-3);
					} else {
						ans.push(motor-2);
					}
				},
				_ => ans.push(motor-2)
			}
		}
	}
	ans
}

/// For use in building TRKS chunks, allowing us to get a sector key for
/// the track's address fields, even if the TMAP/FLUX chunks are something wild.
/// This can be thought of as inverting the map.
/// `slot` is the index into the TRKS array (the value of the TMAP/FLUX entry to search for).
/// Returns `Some((motor_pos, hood, is_flux))`, or `None` if there are no entries for `slot`.
/// Can panic if arguments are invalid.
pub fn get_trks_slot_id(vol: u8,slot: usize,tmap: &[u8],maybe_fmap: Option<&[u8]>,kind: &super::DiskKind) -> Option<(u8,SectorHood,bool)> {
	let mut candidates = Vec::new();
	let mut is_flux = Vec::new();
	for i in 0..tmap.len() {
		if let Some(fmap) = maybe_fmap {
			if fmap[i] as usize == slot {
				candidates.push(i as u8);
				is_flux.push(true);
				continue;
			}
		}
		if tmap[i] as usize == slot {
			candidates.push(i as u8);
			is_flux.push(false);
		}
	}
	let which = match candidates.len() {
		0 => return None,
		1 => 0, // just one choice
		// _ if candidates[0] % 4 == 0 => 0, // if first is a whole track take it
		_ if candidates[1] - candidates[0] > 1 => 0, // if first has nothing adjacent take it
		_  => 1, // otherwise prefer center of head
	};
	let motor = match *kind {
		super::DiskKind::D35(_) => candidates[which]/2 as u8,
		_ => candidates[which]
	};
	Some((motor,get_sector_hood(vol,candidates[which] as usize,kind,0),is_flux[which]))
}

/// Guess a standard format based on the disk kind
pub fn kind_to_format(kind: &super::DiskKind) -> Option<DiskFormat> {
	match *kind {
		super::names::A2_DOS32_KIND => Some(DiskFormat::apple_525_13(9)),
		super::names::A2_DOS33_KIND => Some(DiskFormat::apple_525_16(10)),
		super::names::A2_400_KIND => Some(DiskFormat::apple_35(1,4)),
		super::names::A2_800_KIND => Some(DiskFormat::apple_35(2, 4)),
		_ => None
	}
}

/// Display aligned track nibbles to stdout in columns of hex, track mnemonics
pub fn track_string_for_display(start_addr: u16,trk: &[u8],fmt: Option<&ZoneFormat>) -> String {
	let mut ans = String::new();
    let mut slice_start = 0;
	let mut last_marker = 0;
	let mut last_marker_end = 0;
    let mut err_count = 0;
    loop {
        let row_label = start_addr as usize + slice_start;
        let mut slice_end = slice_start + 16;
        if slice_end > trk.len() {
            slice_end = trk.len();
        }
        let mut mnemonics = String::new();
        for i in slice_start..slice_end {
			if let Some(zfmt) = fmt {
				mnemonics.push(zfmt.woz_mnemonic(trk, i, &mut last_marker, &mut last_marker_end));
			} else {
				mnemonics.push('.');
			}
			if mnemonics.ends_with('?') {
				err_count += 1;
			}
        }
        for _i in mnemonics.len()..16 {
            mnemonics += " ";
        }
        write!(ans,"{:04X} : ",row_label).expect(RCH);
        for byte in trk[slice_start..slice_end].to_vec() {
            write!(ans,"{:02X} ",byte).expect(RCH);
        }
        for _blank in slice_end..slice_start+16 {
            write!(ans,"   ").expect(RCH);
        }
        writeln!(ans,"|{}|",mnemonics).expect(RCH);
        slice_start += 16;
        if slice_end==trk.len() {
            break;
        }
    }
    if err_count > 0 {
        writeln!(ans).expect(RCH);
        writeln!(ans,"Encountered {} invalid bytes",err_count).expect(RCH);
    }
	ans
}